This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The Microarray Core Facility (MCF) provides a specialized method of measuring the expression of thousands of genes simultaneously. This can be extremely useful in characterizing the molecular reactions to diseases, toxic insults and other external stimuli. The MCF has large libraries of genetic information available to identify the genes involved in such reactions. This gives us the capability of measuring the expression of tens of thousands of genes on a single microscope slide by the relative levels of messenger RNA. We provide users with experiment planning and custom microarray printing (if necessary) then proceed through the steps of a standard microarray experiment. RNA is isolated and purified, then converted to more stable cDNA that is labeled with fluorescent dye. This cDNA is measured on a microscope slide with a control sample by a specialized laser scanning microscope. The data is then analyzed to elucidate the response to the given stimulus at the genetic level. This information is then used to determine certain cellular processes or whole tissue responses that may be occurring. This can eventually lead to the identification of a "signature" of genes that respond to a disease or toxin, providing methods of earlier detection or mechanisms of treatment. This is a powerful tool in that it does not require a specific hypothesis that may restrict the scope of an investigator's research. It is considered "hypothesis generating" rather than "hypothesis driven" experimentation.